It is widely believed that he has fresh ambitions to become president of the Commission following a failed bid in 2014, and such an aim would give him an added incentive to deliver a deal viewed as favourable to the remaining 27.

Mr Barnier first locked horns with Brexit Secretary David Davis in the 1990s when they were both Europe ministers.

His appointment to the role of EU chief Brexit negotiator by Commission president Jean-Claude Juncker was viewed as an aggressive move.

Mr Barnier was dubbed the “most dangerous man” in Europe in some quarters of the press when he was appointed internal market commissioner with powers over financial regulation in the wake of the financial crash.

He is said to have angered the usually-cool Sir Mervyn King to such an extent during one meeting that the then Bank of England governor was still shaking with rage an hour after it ended.

Mr Barnier, 67, who is married with three children, always insisted the fears about his role in regulating the City were “unfair and unjust” and said he went into the role wanting to “build a compromise”.

He became involved in French politics as a teenager and later came to prominence after running the successful bid to secure the 1992 Winter Olympics for his country.

A key figure in centre-right politics, he served as minister for the environment, European affairs, foreign affairs and agriculture under presidents Jacques Chirac and Nicolas Sarkozy.

He was named special adviser for defence and security by Mr Juncker last year and released a paper calling on Brussels to “respond to the security imperatives of today and achieve tangible progress in charting a course towards a common Union defence policy for the future”.